Wireless products and services have continued to expand to the point that finite resources of available communication spectrum are being overwhelmed. Industry has been forced to make dramatic changes, as it must adapt to accommodate the exponential demand on spectrum access, efficiency and reliability.
The Federal Communications Commission (FCC) in the United States, and its counterparts around the world, allocate radio spectrum across frequency channels of varying bandwidth. Various bands may cover, for example, broadcast radio, television, cellular phones, citizen's-band radio, pagers and so on. As more devices go wireless, an increasingly crowded radio spectrum needs to be shared. Although the radio spectrum is almost entirely occupied, based on current methods of fixed spectrum allocation and licensing, not all devices use portions of the licensed radio spectrum at the same time or location. At certain times, a large percentage of the allocated spectrum may be sitting idle, even though it is officially assigned and accounted for.
Cognitive radio is a paradigm for wireless communication in which either a network or wireless device alters its transmission or reception parameters to avoid interference with licensed or unlicensed incumbent users. Cognitive radios must implement methods to avoid selecting an occupied frequency, so as to avoid interference to the incumbent device. Cognitive radio systems utilizing several base stations present additional challenges to spectrum sharing in terms of coordination and management that avoids interference amongst both the cognitive network itself and the incumbent system.
Accordingly, it would be highly desirable to optimize spectrum sharing amongst cognitive radio systems and incumbent systems, particularly in the case of multiple cognitive base stations.
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